The massive proposed development on the Cargill salt ponds will either make the mid-Peninsula a commuter’s nightmare or ease the gridlock by taking long-distance drivers off the roads.

Those competing views of the planned 12,000-home Saltworks development’s impact on transportation — the subject of a city meeting this week — reflect a central issue in the debate over the project, which includes 1 million square feet of office space, new parks and more than 400 acres of restored wetlands.

Cargill and developer DMB Associates argue the region needs to build new housing to give commuters coming from places such as Stockton more options to live closer to workplaces.

“By bringing housing near that existing job base, you’re taking away that congestion that is already there, that is already a problem for everybody,” DMB Vice President David Smith said.

But opponents of the projects in surrounding Peninsula cities fear it will add to traffic on roads beyond the 1,436-acre Bayfront site.

“They can’t fix the lack of public transportation in the area,” said Menlo Park City Councilman Andy Cohen, whose group voted to oppose the project.

While city officials are preparing to do in-depth environmental studies of traffic and other issues, traffic projections say there will be 60,000 to 70,000 daily car trips from the site, which is just east of U.S. Highway 101 and south of Seaport Boulevard.

That includes 6,000 to 7,000 trips during peak morning and afternoon commute periods, according figures developed last year by traffic consultant Fehr and Peers. The peak-hour flow on Highway 101 is 13,000 vehicles, according to Caltrans data.

Smith said those traffic estimates don’t adequately take into account the developer’s plans for emphasizing employer shuttles, bicycle sharing and other alternatives to driving.

Residents will be asked to weigh in Wednesday on the project’s potential impacts on transportation, greenhouse gases, noise and air quality at a city-led “scoping” meeting.

The environmental studies will consider the developer’s argument around bringing housing closer to jobs and “put some analysis behind that to make sure those assertions are correct,” Senior Planner Blake Lyon said.

Cargill and DMB point to city figures that show 40,591 people commute into Redwood City for work. In addition, 85 percent of Redwood City workers leave the city for work.